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Do I need ISA DMA when re-creating a new retro PC?
Posted: Tue May 18, 2021 11:51 pm
by technix
As the title suggest, I am thinking about creating a new retro PC using some NOS NEC V20 chips and make it DOS compliant. Given that I have no plan of supporting any kind of floppy (Instead I have a USB interface chip that supports sector-level and file-level access to USB mass storages,) I use XT-SATA hard card (XT-IDE + a JMicron IDE to SATA chip + mSATA SSD all on one board) for local mass storage, and my board uses modern SRAM for system memory (which means no DRAM refresh,) do I even need to have the 8037 ISA DMA onboard?
Re: Do I need ISA DMA when re-creating a new retro PC?
Posted: Wed May 19, 2021 11:16 am
by nullplan
Sound? I do seem to remember the SoundBlaster cards requiring DMA. At least, I haven't found any PIO drivers. Of course, if you plan on only beeping the Speaker then that's not an issue.
Re: Do I need ISA DMA when re-creating a new retro PC?
Posted: Wed May 19, 2021 9:15 pm
by Octocontrabass
Making hardware that boots DOS is easy: you just need an x86 CPU and something vaguely resembling a BIOS. DOS doesn't actually care too much about PC hardware.
Software that runs on DOS tends to care a lot more about PC-compatible hardware. However, thanks to IBM's "clever" hardware design, the DMA controller is used almost exclusively for peripherals like the floppy disk controller or the SoundBlaster. If you're not going to support peripherals that use DMA, you don't need a DMA controller. (You might need something that pretends to be a DMA controller to satisfy software that wants to fiddle with it, though.)